The present invention relates to a recording and reproducing device for use with a magneto-optical recording medium, and more particularly to a magneto-optical recording and reproducing device which is arranged so that it is able to simultaneously perform a plurality of operations such as erasing, recording and reproducing and to make up the shortage of power for erasing and recording.
Conventional magnetic recording and reproducing devices employing a magneto-optical recording medium are roughly divided into the one-beam type and the three-beam type. The former performs recording and reproducing with one beam and also uses the same beam for tracking. In contrast thereto, the latter employs two beams for tracking use separately of a beam for recording and reproducing and performs tracking servo based on a difference between the two beams as illustrated in U.S. Pat. No. 3,905,040 to Otala. Either system uses the same beam for recording and reproducing. Recording takes place by irradiating the magneto-optical recording medium by a laser beam to raise the temperature of the irradiated portion, reducing its coercive force to cause a reversal of magnetization of that portion to the direction of the magnetic field. On the other hand, reproducing is performed by irradiating the recording medium by the same beam weakened to such an extent as not to destroy the record and detecting the rotation of the plane of polarization of reflected or transmitted light from the medium in accordance with the direction of its magnetization. The magneto-optical recording medium makes a great feature of arbitrary erasing and restoring of records. According to the prior art system, in the case of storing new information in a recording medium having already recorded thereon information, a portion of a recording track where the new information is to be recorded is entirely scanned by a beam in the presence of a homogeneous magnetic field perpendicular to the surface of the medium to lower its coercive force, directing the magnetization of the medium to the same direction as the ambient magnetic field. This corresponds to erasing. Next, a magnetic field opposite in direction to that employed for erasing is applied to the recording medium to store thereon the new information on the aforementioned principle. For checking whether or not the information has been correctly recorded, it is necessary to reproduce the entire recorded information. The conventional system thus employs the same beam for all of the erasing, recording and reproducing operations, and consequently it has the defect that only one operation can be performed at one time.